Immersion lithography is rapidly emerging as an important microelectronics fabrication technology. In immersion lithography a liquid is placed between the last optical element of the immersion lithography tool and photoresist layer. The optical properties of the liquid allow improved resolution and depth of focus to be attained. One key issue associated with immersion lithography is that the potential exists for photoresist degradation and for contamination of the optical components through leaching of photoresist components into the liquid layer. Topcoat materials applied over the resist layer are being examined as a means of suppressing this extraction.
Two types of topcoats currently exist. The first types of topcoats are water-insoluble requiring a topcoat stripping process prior to photoresist development. The second types of topcoats are water-insoluble but aqueous-base soluble which are readily removed during photoresist development but have the problem of tending to dissolve the photoresist layer and leave interfacial layers where the photoresist and topcoat layers were in contact.
Therefore, there is a continuing need for improved topcoat materials and methods of forming topcoat layers.